Precision cutting of metal bars is usually carried out by means of a hacksaw, which is power operated by any suitable power source, and reciprocates to and fro.
This cutting method is slow and costly, and may be limited as to the depth of cut that can be made.
However, the speed of cutting is restricted by the type of metal, and its hardness, and also by the physical limitations of the hacksaw blade itself.
Clearly, it is desirable as far as possible to speed up the rate of cutting of such metal bars, provided this can be done without loss of accuracy.
Typically, known hacksaw apparatuses are driven by an engine or motor operating through a mechanical transmission means. When the hacksaw blades of such apparatuses contact a workpiece, the force of the blade against the workpiece varies throughout the stroke. The speed of the blade also varies througout the stroke. In order to apply a more constant force to the workpiece and to move the blade at a more constant speed, bulkier, and heavier and more complex transmissions would be required.
Furthermore, the return stroke of a hacksaw blade during which no cutting takes place generally takes the same amount of time as the cutting stroke. The maximum speed of the blade during the cutting stroke is pre-determined by factors such as the blade design, workpiece material and cutting lubricant. Thus, in order to increase the speed of operation of the hacksaw apparatus, only the speed of the blade during the return stroke may be increased. However, in order to achieve such function, the transmission must again be made bulkier, heavier and more complex.
Of course, such increases in the size and weight of the hacksaw apparatus add further cost to the machine. As well, surrounding support structure, such as a machine foundation, may have to be provided with increased capacity, also at additional cost.
A further disadvantage of known hacksaw apparatuses is that the stroke length of a hacksaw blade is fixed. Thus, for workpieces of varying heights only a portion of the available blade length may be utilized in cutting operations. Such limitation results in excess wear of a blade in particular areas and of reduced blade life. In order to overcome this disadvantage, further weight, bulk, complexity and expense would be required in the transmission means.
Finally, most known hacksaw apparatuses include only a single hacksaw, operable therefore only to cut a workpiece from one side only. Such devices are relatively slow in operation because they can only cut from one side. Known hacksaw apparatuses having two hacksaws are very bulky and heavy. The mechanical complexities of single hacksaw machines are compounded by having two opposed hacksaws.
The invention thereforeprovides two essentially parallel spaced apart hacksaw blades, mounted on reciprocating support means in opposition to one another, which can be operated simultaneously so as to cut a bar from both sides at once.
In accordance with a further objective of the invention, a table is provided adjacent to such saw blades and frames, and clamping means are provided for clamping a work piece on the table.
More specifically, the invention provides two such saw frames, slidable guide means for sliding such saw frames towards and away from one another, said slidable guide means being reciprocable in a plane normal to the plane of such sliding movement, and power operated means for reciprocating said guide means and frame means in unison relative to a work piece.
More specifically, the power operated means will comprise at least two, and preferably four, hydraulic cylinders, and mechanical linkage means connected with said four cylinders and with said slidable guide means, whereby to equalize movement of said slidable guide means in response to operation of said cylinders.
More specifically, the invention provides a saw apparatus having the foregoing advantages in which the slidable guide means for guiding the blade frames are slidable towards and away from one another, by power operated means, such power operated means being mounted on said slidable guide means, and being reciprocable in association therewith.
Consequently, it would be advantageous to provide a double hacksaw apparatus, the blades of which are operable to apply a relatively constant force to a workpiece during a cutting stroke. Furthermore, such blades ought preferably to have a more constant velocity during the cutting stroke in order to increase the overall speed of the cutting operation and in order to improve the efficiency of the cutting stroke. Such advantages should be obtained, if possible, without adding to the bulk, weight or expense of the hacksaw apparatus.
It would also be advantageous, if the speed of the return stroke of the hacksaw apparatus could be increased, again without adding to bulk, weight or cost.
Similarly, it would also be advantageous to provide a hacksaw apparatus operable to use the full available length of a hacksaw blade, in order to improve cutting operation and blade life.